Forging machine



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United States Patent O 3,14%,642 FQRGHNG MACHENE Bruno lralewetz, St. Ulrich, near Steyr, Austria Filed (lan. 3, 1963, Ser. No. 249,28 Claims priority, application, Austria, Feb. 14, 1959, A 1142/59 13 Claims. (Cl. 73-22l This application is a continuation-in-part of application Serial No. 4,770, tiled January 26, 1960, entitled Forging Machine, and now abandoned.

This invention relates to a forging machine which comprises hammers formed by connecting rods driven by eccentric shafts which are eccentrically mounted in housings, which are rotatably mounted and angularly adjustable by means of a hydraulic piston drive. By an angular adjustment of these housings with the aid of the hydraulic piston drive, the hammer tools are caused to approach or move apart from each other in order to determine the desired cross-sectional dimensions of the workpiece which is moved between the hammers and at the same time may be rotated about its axis. Exact forgings can only be obtained if the housings are always angularly adjusted exactly to that position which corresponds to the diametral size of the workpiece. Because the angular movement of the adjusting housings is effected by the hydraulic piston drive, the displaceable part of this piston drive must be moved exactly to the respectivepredetermined position.

The movement of the displaceable part of the hyraulic piston drive has previously been terminated only by a control operation in the hydraulic system. it has now been found that this involves certain factors which impair an exact stopping of the drive particularly because large forces due to mass are usually effective, further, because different speeds may be employed (high-speed and lowspeed motions) and because leaks and the like in the hydraulic system may also constitute sources of error.

For this reason, it is an object of the invention to irnprove the known forging machines of the type described so that the `adjusting movement of the housings which contain the eccentric shafts for driving the hammers, and consequently the setting movements of the hammers towards and apart from each other (closing and opening movements) correspond exactly to the desired dimension so that more exact forging is obtained.

The invention resides essentially in that a stop which is adjustable by an electric motor is provided to limit the movement of the displaceable part of the hydraulic piston drive in the direction corresponding to a closing movement of the hammers and that this part of the piston drive is hydraulically urged against this stop during the Working blows of the hammers, further, that the motor for driving the stop is energizable by means of an electric control device and deenergizable by limit switches and the control device adjusts at the same time valves in the hydraulic system connected to the piston drive.

The position of the mechanically adjustable stop can be exactly predetermined at any time because the forces due to mass which act on the stop can be conveniently controlled, further, because the stop is always moved at the same speed and the disadvantages of a hydraulic system do not arise. The stop determines exactly the stroke position of the hammers and the depth of their penetration into the workpiece. The hydraulic pressure acting on the displaceable part of the piston drive ensures that this displaceable part will actually assume exactly the position predetermined by the stop. This results in the further advantage that this displaceable part is forced during the working blows against a xed abutment and is thus clamped in position so that undesired adjusting movements cannot occur. Because the pressure is applied by a liquid, a hydraulic buffer is obtained which can yield to some extent in the case of vibration and backstrokes. It must be borne in mind that the reaction forces due to the forging forces tend to rotate the adjusting housings in a sense corresponding to an opening movement of the hammers. This tendency is opposed by the pressure whereby the displaceable part ofthe piston drive is forced against the stop. This is a very important improvement because special provisions were previously necessary to ensure that the housings were self-locking in the forging box as far as possible. Besides, the electric control device results in a simplification of the structure of the machine, particularly because the hydraulic system Was previously controlled by purely mechanical means.

A rotary valve or the like which rotates in synchronism with the driving eccentric shafts for driving the hammers may be incorporated in the hydraulic conduit for operating the piston drive in the hammer closing direction, which rotary valve closes this conduit during the last phase of the approaching or striking movement of the hammers. During those intervals of time in which the hammers strike on the workpiece and in which the reaction forces occur, the space in which the hydraulic buffer is disposed is then closed and the adjusting housings cannot be rotated by the reaction forces because they had to compress the trapped hydraulic buffer. Any sudden movement of the displaceable part of the piston drive which may result from the incorporation of the rotary valve can be tolerated.

An embodiment of the invention is shown by way of example in the accompanying drawings, in which FIG. 1 is a side View on a reduced scale showing the entire forging machine.

FIGS. 2 and 3, respectively, show the forging box with the hammer drive in a sectional View taken on line II-II (left-hand half of FIG. 2) or IIa-Ila (right-hand half of FIG. 2) of FIG. 3 and in a sectional view taken on line III-III of FIG. 2.

FIGS. 4 and 5, respectively, are an elevation and a sectional view taken on line V-V of FIG. 4 and show the device for setting the hammers.

FIGS. 6 and 7 are sectional views taken on lines VI-VI and VII-VII, respectively, of FIG. 5, and show details of this device.

FIG. 8 shows diagrammatically the hydraulic system for setting the hammers and FIG. 9 is a circuit diagram of the electric control device.

The forging box 1 accommodates the hammers 2, which consist of connecting rods. The connecting rods 2 are driven by eccentric shafts 3, which are eccentrically mounted in housings 4, which are angularly adjustably mounted in the forging box 1. The housings 4 are provided each with a gear rim 5. The gear rims 5 are in mesh with a central gear 6, which is in mesh with a pinion 7, a rotation of which causes through the intermediary of the central gear 6 a rotation of the adjusting housings 4 so that the eccentric shafts 3 being eccentrically mounted in the housings 4, are moved toward or away from each other to change the stroke position of the hammers and the depth of penetration of the tools into the workpiece. The eccentric shafts 3 are driven by a common motor 8, which drives a gear 9, which is coupled to one shaft 3 and through the intermediary of idler gears 10 drives gears 11, which are similarly coupled to the other eccentric shafts.

The workpiece is gripped by a gripping head 12, which is slidable on a bed 13. For this purpose the gripping head 12 is connected to the rod 14 of a piston 15 slidable in a cylinder 16. In response to the application of hydraulic pressure to one end or the other of piston 15, the gripping head 12 will be advanced toward the forging a n.7) box 1 or retracted from the same. By means of a motor 17 the workpiece can be rotated about its axis.

By a shaft 18, the pinion 7 is connected for joint rotation with another pinion 19, which is in mesh with a displaceable cylinder 2) formed as a rack. A displacement of the cylinder 20 will thus cause a rotation of the central gear 6 and of the housings 4 and consequently a change in the stroke position of the hammers and of the depth setting of the hammer tools. In FIGS. 4, and 8 the upward movement of the cylinder 2) corresponds to a closing movement of the hammers whereas a downward movement of the cylinder causes the hammers to be opened.

The cylinder contains the stationary piston 21, the piston rod 22 of which contains hydraulic conduits 23, 24. The conduit 23 opens below the piston 21. On this side of the piston the rod 22 is larger in diameterthan on the other (upper) side, where the conduit 24 opens. Pressure is permanently applied through conduit 23 so that the cylinder 20 tends to move downwardly, in the hammer opening direction. The effective piston face at the top of the piston being larger, the cylinder 20 will move upwardly, to adjust the hammers in the closing sense, if pressure is applied on this side. The oil or the like which is displaced from the cylinder chamber below the piston 21 is then urged back into the conduit system.

Whereas the hydraulic piston drive formed by the cylinder 20, the piston 21 and the piston rod 22 could alternatively be arranged so that the piston and the piston rod move and the cylinder is stationary, the use of the cylinder as the displaceable part has the advantage that the overall length is reduced. The permanent application of pressure through the conduit 23 results in a simplication of the control system, particularly for the emergency operation to open the hammers.

The cylinder stroke in the hammer opening direction is limited by a stop ring 25, a plate spring 26 for damping the impact on the stop, and a flange 2S firmly connected to the guide housing 27 of the cylinder 20. To limit the cylinder stroke in the upward or hammer closing direction, a stop is provided which can be adjusted by an electric motor throughout the length of the stroke and which consists of a screw sleeve 30 which is mounted on the piston rod 22 provided at its upper end with a screw thread 29. This screw sleeve carries a stop head 31 which is supported by a thrust bearing and held against rotation by a driver 39, which in turn is constrained to move along a longitudinal slot in housing 27. The screw sleeve 30 is connected for rotation with a worm wheel 32 so as to be longitudinally displaceable relative thereto. A worm 33 in mesh with the worm wheel 32 is driven by a motor 34 by means of an electromagnetic clutch 35, 36 designates a spring pressureapplied multiple plate brake which can be electromagnetically lifted and which is automatically applied when the clutch is disengaged and which is lifted when the clutch is engaged. The sleeve 30 follows a rotation of the worm wheel 32 and owing to the threaded connection of the sleeve to the piston rod 22 this rotation causes a longitudinal adjustment of the sleeve. The bearings of the worm wheel 32 need not take up axial forces when the cylinder 20 strikes the stop 31 as such forces will be transmitted to the piston rod 22 owing to the threaded connection. The worm shaft may extend outwardly through the brake 36 and may be used here for a manual adjustment of the stop after a switch has been operated to` lift the brake. The stop 31 determines the position of the cylinder 20, which in its position of rest is always hydraulically urged against the stop. The clutch 35 and the brake 36 are provided to ensure an exact positioning of the stop and to prevent an undesired adjustment when the cylinder strikes against the stop.

The valves in the hydraulic system connected to the piston drive 20, 21 are electrically operated. Various limit switches and a control device consisting of a stepiae ping switch are provided for this purpose. The limit switches are actuated by cams, which can be set in different positions and determine the extent of the setting movement of the hammers. As the stop 31 determines the extent of the hammer setting movement, the associated control plate 37, in which the cams 38 are inserted in parallel longitudinal grooves, is not connected to the cylinder 2) but is connected to the stop head 31 by the driver 39 extending through a slot formed in the housing 27. Hence, the control plate 37 slidably mounted on the guide housing 27, moves together with the stop 31. The limit switches 41 operable by the cams 38 are secured to a stationary transverse bridge 4t).

As the stop cannot be moved against the cylinder 20 forced against the stop and the latter when arrested must be perfectly free from loads applied by the cylinder, different speeds are selected for 'the adjustment of the stop and for the displacement of the cylinder, so that the stop 31 and the cylinder 2G can move apart. When the stop 31 is arrested by a limit switch 4l operated by the cam 38, the cylinder 20 will be in a position which cannot be predetermined and the cylinder must again move into engagement with the stop head 31 before a movement of the stepping switch to another control stage is permissible. To achieve this, an additional limit switch 42 is arranged on the stationary bridge 4t). The control plate 37 carries also a rail 43, which is pivotally movable about its longitudinal axis and which is provided at its lower end with a head 44, which has a beveled surface 45. Slidably arranged on 'the housing 27 is another plate 46, which is connected to the cylinder 2t) 'oy a driver, which extends also through a longitudinal slot in the housing 27. This plate t6 carries at its upper end a roller 47, which runs up on the beveled surface 45 of the rail head 44 shortly before the cylinder 20 engages the stop head 31. Thus, 'the rail d3 is pivotally moved to press the additional limit switch 42, which then initiates the next step of the stepping switch.

FIG. 8 shows the hydraulic system for applying pressure to the piston drive 20, 21. The pressure oil supplied by a pump 48 may tlow through the conduit 23 to the side below the piston 21 and through the conduit 24 into the chamber over the piston. In the position shown, the conduit 24 is closed by the magnetic slide valve 49 so that the oil can flow from the chamber over the piston through the slide valve 49. The conduit 23 supplies pressure oil into the chamber below the piston 21 so that the cylinder 2@ will descend to move the hammers apart or to open them.

When the magnetic slide valve 49 is moved to the right, an uninterrupted pressure conduit is established to the chamber' over the piston 21, as is indicated by the arrows in the drawing. As the effective piston area on this side of 'the piston is larger, the oil disposed below the piston is urged back into the conduit 23 and the cylinder 20 moves upwardly until it strikes the stop 31. By this movement, the hammers are approached to each other or closed. When the magnetic slide valve 50 is in the posiltion shown, the oil can be urged back through the unthrottled conduit 23 so that the hammers are closed more quickly. On the other hand, if the slide valve 50 is moved to the right, the oil urged out of the space below the piston 21 must flow through conduit 51 and throttle 52 so that the hammers close more slowly.

The conduit 24 incorporates also a rotary valve 53, which rotates in synchronism with the eccentric shafts 3 driving the hammers to close the conduit 24 whenever the hammers are at the end of their approaching or impact movement. In this case, the oil over the piston 21 forms a buffer in a closed space and the reaction forces due to the forging forces cannot cause an adjustment of the bearing housings for the driving eccentric shafts in the sense of the hammer opening movement.

A similar hydraulic system is provided for controlling the alternating application of hydraulic pressure to the L" el) opposite ends of the piston in the cylinder 16 for moving the gripping head.

FIG. 9 is a circuit diagram of the stepping switch. Only the circuitry for setting the hammers (left-hand part of the figure) and for the sequential stepping movement (right-hand part of the figure) are shown. The switch arm 54 moves, eg., over seventeen contacts 55, the last of which corresponds to the zero position, from which the switch arm is immediately moved to the first contact when the machine is started or a repeat button 56 is pressed. It is apparent that the limit switches 41 lie in lines 57 coming from the contacts 55 so that these lines will be interrupted when the limit switches 41 are pressed. During each control stage serving to adjust the hammers, the stepping switch 54, 55 has control lines 58, 59, 61B connected to it, which control lines incorporate selector contacts 61 and lead to relays 62, 63, 64. It is obvious that any of relays 62, 63, 64 will be energized only when one of the selector contacts 61 is closed in the respective control stage to which the switch arm 54 is se't. When the forging program is determined beforehand, the selector contacts are closed from the beginning by the insertion of plugs. A mechanical interlock is provided so that in each control s'tage only one selector contact can be closed by the insertion of a corresponding plug and only one relay can be connected in circuit. Those contacts 55 of the stepping switch which are shown without leads in FIG. 9 are also connected by selector contacts to relays serving for controlling the valves in the hydraulic system for displacing the gripping head. Because the specific control of the displacement of the gripping head is not a subject matter of the invention and the displacement of the gripping head can be controlled by alternative means, the circuitry required for this purpose has been omitted for the sake of clarity.

In the control stages for setting the hammers, line 58 is associated with the high-speed opening movement of the hammers, line 59 with the high-speed closing movement and line 60 with the low-speed closing movement. For this reason, the energization of relay 62 causes by means of the normally open contact 65 the electric motor 34, serving to move the stop 31, to be energized for rotation in a direction so as to lower the stop and at the same time causes an engagement of the clutch and a lifting of the brake 36 whereas 'the energization of the relays 63, 64 causes by means of their normally open contacts the motor 34 to be energized for rotation in the opposite direction. The normally open contact 68 of relay 64 is operable to close a circuit to move 'the slide valve 50 to the right so that the return liow of the pressure oil from the conduit 23 takes place through the conduit 51 and the throttle 52. As a result, the closing movement is throttled to be performed at a lower speed.

If the selector contact 61 in the line 59 or 60 is closed in the first control stage for setting the hammers` and when the switch arm 54 has reached the third contact, the relay 63 or 64 will be energized and the stop 31 will be adjusted lalone whereas the hammers are in the fully opened position. As soon as the rst cam 38 presses the rst limit switch 41, the stop will be arrested because the circuit leading to relay 63 or 64 is interrupted. The pressing of the respective limit switch 41 closes a second contact 41a of this switch whereby the line 69 is closed and the relay 70 is energized. The relay 70 operates its normally open Contact 71, which through the line 72 energizes the slide valve 49 for movement to the right to cause hydraulic pressure to be applied to the piston drive 20, 21 in the hammer closing direction. As a result, the cylinder 2t) is lifted and strikes the adjustable stop 31. This enables the position of the cylinder 20 to be determined by the same stop 31 even after an opening movement of the hammers. By means `of the normally open contact 73 the relay 70 is now holding itself so that the position of the control device and slide valves is maintained and the cylinder 20 is permanently urged against the stop 31.

When in another control stage the selector contact 61 in line 58 is closed to cause the hammers to open, the relay 62 will be energized as soon as the switch arm 54 has reached the Iappertaining contact 55. The relay 62 will then close its normally open contact 65 and at the same time open the normally closed contact 74 in the circuit of relay 70, which is thus deenergized so that its normally open contacts 71, 73 return to the normal position shown. As a result, the slide valve 49 returns also to its position of rest shown in FIG. 8 so that the cylinder 2t) descends and the hammers are opened. The normally open contact 65 of relay 62 causes the motor 34 to be energized so as to lower the stop. When the stop has reached the desired end position so that the associated limit switch 41 is pressed, the interruption of line 58 causes the relay 62 to be deenergized so that the contact 74 returns to its closed normal position. At the same time, however, the auxiliary contact 41a of the respective limit switch 41 has closed so that the relay 70 is connected in circuit by the line 69 and contacts 41a and 74. The normally open contact 71 is now closed to energize the slide valve 49 through the line 72 to move to the right so that the piston drive 2t), 21 is moved in the hammer closing direction and is displaced against the arrested stop until the hammers have assumed the stroke position determined by the stop. Thus, the hammers are closed to the desired position corresponding to the adjustment of the stop 31 after each setting movement of the hammers regardless of the direction of said movement.

The limit switches 41 should also initiate the stepping movement of the switch arm 54. For this reason lines 75 lare provided, which include each another auxiliary contact 41b of the limit switches 41 and these contacts 41h are closed only when the respective limit switch 41 is pressed a-t the end of a setting movement of the hammers. The lines 75 lead to a line 76, to which the stepping mechanism 77 is connected. From the right-hand part of FIG. 9 the arrangement of the limit switch 42 is apparent, which lies in line 76 in series with the auxiliary contacts 41h of the limit switches 41. This indicates that the stepping mechanism 77 will not operate to move the stepping switch to the next stage until one of the limit switches 41 and in addition thereto the switch 42 are pressed.

What I claim is:

1. A forging machine which comprises hammers consisting of connecting rods, eccentric shafts operable to cause said connecting rods to perform `a working motion in intervals, housings eccentrically mounting said eccentric shafts, a forging box rotatably mounting said housings, a hydraulic piston drive having a displaceable part movable in opposing directions, said housings, being angularly movable in a closing sense to cause said hammers to perform a setting movement in a closing direction, and being angularly movable in an opening sense to cause said hammers to perform a setting movement in an opening direction, means operatively connecting said displaceable part to said housings to cause an angular movement of said housings in a closing sense in response of a movement of said displaceable part in one of said opposing directions and an angular movement of said housings in an opening sense in response to a movement of said displaceable part in the other of said opposing directions, a hydraulic system operable to apply hydraulic pressure to said piston drive and including valve means for controlling the application of pressure to said piston drive, said valve means being movable between rst and second positions, in which they cause hydraulic pressure to be applied to said piston drive to urge said displaceable part in said one and said other of said opposing directions, respectively, said machine further comprising a stop adapted to limit the movement of said displaceable part in said one of said opposing directions and adjustable in said opposing directions, and a reversible electric motor energizable to adjust said stop.

rasees 2. A forging machine as set forth in claim 1, in which said working motion comprises closing and opening strokes and said hydraulic system comprises a hydraulic conduit for applying hydraulic pressure to said piston drive to urge said displaceable part in said one of said opposing directions, said conduit comprising further a valve means arranged to operate in synchronism with said eccentric shafts and to close said conduit during a nal phase of each closing stroke.

3 A forging machine as set forth in claim 1, in which `said further valve means comprise a rotary valve arranged to rotate in synchronism with said eccentric shafts.

4. A forging machine as set forth in claim 1, in which said piston drive comprises a stationary piston and a cylinder consisting of a rack and forming said displaceable part, and in which said hydraulic system is arranged permanently to apply hydraulic pressure to said piston drive so as to urge said displaceable part in said other of said opposing directions, said piston having a piston rod protruding from both ends of said piston and larger in diameter at that end of said piston to which hydraulic pressure is permanently applied.

5. A forging machine as set forthin claim 4, in which said piston rod has a screw thread and said stop comprises a screw sleeve threaded to said screw thread and a stop head freely rotatably mounted on said sleeve, and which comprises a worm connected to said motor, and a worm wheel in mesh with said worm and connected for rotation with said sleeve, which is longitudinally movable relative thereto.

6. A forging machine as set forth in claim 1, which comprises an electrically operable clutch connected b etween said motor and said stop, an electrically liftable brake for said stop, means tending to apply said brake, and means for controlling said brake in dependence of said clutch whereby said brake is electrically lifted when said clutch is engaged and said brake is automatically applied when said clutch is disengaged.

7. A forging machine as `set forth in claim 1, which comprises an electric sequence control device adapted to control the energization and the direction of rotation of said motor and the position of said valve means, said control device including limit switch means operable to deenergize said motor, said machine further comprising adjustable means arranged to operate said limit switch means in response to a preselected movement of said stop, said control device being operable to perform a sequence of control operations comprising energizing said motor to cause said stop to perform said preselected movement, causing said valve means to assume said first position, holding said valve means in said first position until the next interval of working motion has been completed, and then causing said valve means to assume said second position.

8. A forging machine as set forth in claim 7, in which said limit switch means comprise a plurality of limit switches arranged in a row and said adjustable means comprise a control plate arranged to be moved in a direction which is transverse to said row in response of the movement of said stop, said control plate having a plurality of grooves extending in said transverse direction,

LJ said adjustable means further comprising a plurality of cams, each of which is adjustably fixed in one of said grooves and adapted to engage one of said limit switches in response to said preselected movement of said stop.

9. A forging machine as set forth in claim 8, in which said control plate is connected to said stop and which comprises a stationary bridge mounting said limit switches.

10. A forging machine as set forth in claim 8, in which said electric control device is adapted to energize said electric motor to adjust said stop at a speed which is different from the speed imparted at the same time to said displaceable part by the application of hydraulic pressure to said piston drive and said electric control device comprises a stepping switch having a series of contacts and a movable Contact member movable in successive steps from one of said contacts to the next, said electric control device further comprising a plurality of stepping lines, each of which is connected between one of said contacts and one of said limit switches, additional limit switch means connected in series with said stepping lines and arranged to be closed in response to the movement of said displaceable part shortly before it moves into engagement with said stop, and stepping means energizable to cause said stepping switch to perform one of said successive steps, said stepping means being arranged to be energized when said additional limit switch means as well as the limit switch connected to the stepping line which is connected to the contact then engaged by said movable contact member are closed.

11. A forging machine as set forth in claim 10, which comprises a stationary bridge mounting said limit switch means and said additional limit switch and which comprises a rail connected to said control plate to move in unison therewith, said rail being arranged to be engaged by said displaceable part shortly before the latter moves into engagement with said stop, and said rail being arranged to be pivoted about said axis and to close said additional limit switch in response to the engagement of said rail by said displaceable part.

l2. A forging machine as set forth in claim ll, in which said rail is formed with a beveled surface and said displaceable part carries a roller arranged to engage said beveled surface shortly before said displaceable part moves into engagement with said stop.

13. A forging machine as set forth in claim 8, in which each of said limit switches comprises a contact arranged to be operated in response to the engagement of the respective limit switch by the respective cam, and in which said electric control system is arranged to move said valve means to said first position in response to the operation of said contact.

References Cited in the file of this patent UNITED STATES PATENTS 2,562,643 Saxer July 31, 1951 2,776,584 Burg Ian. 8, 1957 2,840,170 Best June 24, 1958 2,979,909 Broadbent Apr. 18, 1961 3,035,130 Dachltevitch May 15, 1962 

1. A FORGING MACHINE WHICH COMPRISES HAMMERS CONSISTING OF CONNECTING RODS, ECCENTRIC SHAFTS OPERABLE TO CAUSE SAID CONNECTING RODS TO PERFORM A WORKING MOTION IN INTERVALS, HOUSINGS ECCENTRICALLY MOUNTING SAID ECCENTRIC SHAFTS, A FORGING BOX ROTATABLY MOUNTING SAID HOUSINGS, A HYDRAULIC PISTON DRIVE HAVING A DISPLACEABLE PART MOVABLE IN OPPOSING DIRECTIONS, SAID HOUSINGS, BEING ANGULARLY MOVABLE IN A CLOSING SENSE TO CAUSE SAID HAMMERS TO PERFORM A SETTING MOVEMENT IN A CLOSING DIRECTION, AND BEING ANGULARLY MOVABLE IN AN OPENING SENSE TO CAUSE SAID HAMMERS TO PERFORM A SETTING MOVEMENT IN AN OPENING DIRECTION, MEANS OPERATIVELY CONNECTING SAID DISPLACEABLE PART TO SAID HOUSINGS TO CAUSE AN ANGULAR MOVEMENT OF SAID HOUSINGS IN A CLOSING SENSE IN RESPONSE OF A MOVEMENT OF SAID DISPLACEABLE PART IN ONE OF SAID OPPOSING DIRECTIONS AND AN ANGULAR MOVEMENT OF SAID HOUSINGS IN AN OPENING SENSE IN RESPONSE TO A MOVEMENT OF SAID DISPLACEABLE PART IN THE OTHER OF SAID OPPOSING DIRECTIONS, A HYDRAULIC SYSTEM OPERABLE TO APPLY HYDRAULIC PRESSURE TO SAID PISTON DRIVE AND INCLUDING VALVE MEANS FOR CONTROLLING THE APPLICATION OF PRESSURE TO SAID PISTON DRIVE, SAID VALVE MEANS BEING MOVABLE BETWEEN FIRST AND SECOND POSITIONS, IN WHICH THEY CAUSE HYDRAULIC PRESSURE TO BE APPLIED TO SAID PISTON DRIVE TO URGE SAID DISPLACEABLE PART IN SAID ONE AND SAID OTHER OF SAID OPPOSING DIRECTIONS, RESPECTIVELY, SAID MACHINE FURTHER COMPRISING A STOP ADAPTED TO LIMIT THE MOVEMENT OF SAID DISPLACEABLE PART IN SAID ONE OF SAID OPPOSING DIRECTIONS AND ADJUSTABLE IN SAID OPPOSING DIRECTIONS, AND A REVERSIBLE ELECTRIC MOTOR ENERGIZABLE TO ADJUST SAID STOP. 